Rabbi Meir Kahane had just finished addressing a crowd of supporters at the Marriott East Side Hotel in New York on November 5, 1990, when a man, of Middle Eastern appearance and wearing a kippah, fired a shot at close range. The controversial 58-year-old founder of the ultra right-wing Jewish Defence League fell to the floor, blood gushing from a wound to his neck.

Twenty years on, investigative reporter Peter Lance believes the murder was not the action of a lone radical, but Al Qaeda's first attack on American soil. "That was the first shot in the War on Terror," says Lance, an Emmy award-winning television reporter and author of three books on America and 9/11.

According to FBI documents uncovered by Lance, Kahane was not even the original target of the assassin, El Sayyid Nosair. Rather, Nosair, a janitor at a Brooklyn courthouse, had intended to kill Ariel Sharon, then Israel's minister of housing and construction, who was due to visit New York. In an interview conducted five years ago and revealed in the FBI papers, Nosair told agents that he staked out Sharon's hotel. Later, he abandoned the operation and shifted to Kahane.

The Manhattan District Attorney's office has always characterised Nosair as a lone gunman. But, according to the documents, Nosair was accompanied by a getaway driver and by a Jordanian named Bilal al-Kaisi, who was armed with two guns. Al-Kaisi was later arrested in connection with the 1993 World Trade Centre bombing. However, for reasons still unknown to Lance, he was allowed to plead guilty to minor immigration charges and to leave the US. He has not been seen since.

Following years of research, and interviews with US investigators and Arab sources, Lance has drawn a direct link between Nosair, al-Kaisi and 9/11. The two men both frequented Brooklyn's al Farooq mosque, which shared a building with the Alkifah Centre, a Pakistan-based organisation that raised funds for the Afghan Mujahideen. Lance describes the Alkifah Centre as "a New York clubhouse" for the fledgling Al Qaeda, which was founded towards the end of the 1980s.

Kahane in brief

Born: Brooklyn, New York, 1932. Father was an Orthodox rabbi.
Career in the US: Became an ardent Zionist in his teens. Appointed rabbi at a New York synagogue in 1956. Founded the Jewish Defence League in 1968 to combat antisemitism against American Jews. The group played a leading role in support of Soviet Jewry.
Career in Israel: Emigrated in 1971. Founded the extremist right-wing Kach party, advocating an Arab-free Israel. Elected to the Knesset in 1984.
Assassination: Shot dead by Nosair al-Kaisi in New York in November 1990. His killer received a life sentence.

In the summer of 1990, shortly before Kahane's death, the radical sheikh, Omar Abdel-Rahman, arrived in America. Abdel-Rahman, whom Lance calls "the spiritual head of Al Qaeda", would later become infamous as the mastermind of the 1993 trade centre bombing, in which more than 1,000 people were injured and six were killed. Three of the terrorists convicted of that bombing - Mahmoud Abouhalima, Mohammed Salameh, and Nidal Ayyad - were observed by the FBI at a shooting range with Nosair in the months before the Kahane murder. Abouhalima and Salameh were also with Nosair on the night of the assassination.

Shortly after arriving in the US, Abdel-Rahman began preaching at al Farooq and other mosques. Lance believes he almost certainly inspired Nosair's mission. "I can't get inside Nosair's head, but if this sheikh arrives and you are young and want to be the first guy to take the shot, what would you do? He wasn't able to get Sharon, so he got Kahane," he says.

When the FBI raided Nosair's home, in New Jersey, they found a hit-list of prominent Jewish individuals. It included judges, politicians and others, such as the lawyer and political commentator, Professor Alan Dershowitz. "Meir Kahane's death had a big impact on me," says Dershowitz. "I speak all over and even today, everywhere I speak I need massive security."

Dershowitz and Kahane attended the same yeshivah high school in Brooklyn. "He was an infamous character even then," says Dershowitz, "a strident right-wing Zionist."

Kahane's views were certainly extreme. To some, he remains a hero - a plain-speaking politician who offered no-nonsense ways of cementing Jewish power in Israel. To others, he is a demagogue whose anti-Arab views were reminiscent of Nazism and whose JDL was, at heart, a terrorist organisation.

"His views were on the extreme right," says Dershowitz. "They were, however, consistent with the views of many extremely Orthodox nationalists."

The JDL started life as a community defence organisation and became a violent agitator on behalf of Soviet Jewry during the late 1960s. In 1972, one year after Kahane moved to Israel, the JDL targeted the Jewish impresario Sol Hurok for bringing Soviet performers to the US. The group bombed Hurok's office, killing a secretary.

In Israel, Kahane founded Kach, a far-right party that advocated the expulsion of Arabs and the establishment of a religious Jewish state. His party won a seat in the Knesset in 1984. In the mid-1980s, at a debate, held at Boston University, Kahane defended the killing of Arab civilians. "He who comes to slay you," he quoted from the Talmud, "slay him first."

He also asserted that Israeli-Arabs could never be loyal to a Jewish state - a notion that has surfaced again in the current controversy in Israel surrounding a loyalty oath. Kahane's proposal was to offer financial incentives to Israeli-Arabs who wished to leave and to forcibly remove those who refused.

Though Kahane's meetings were never attended by more than a few hundred supporters, the American-born Israeli commentator Yisrael Medad, who knew the rabbi, believes his views had a wide appeal.

"Kahane would say to me: 'Do you know how many cardiac Jews I have met in my life? They come over to me, tap their chest and say, Rabbi Kahane, in our hearts, we know you are right, but we can't identify with you'."

He argues that Kahane touched on some of the central issues that remain unresolved in Israel today. "His analysis brought him to negate totally the idea of a democratic Jewish state and to go into a radical, religious interpretation of the issues," he says.

Last weekend in New York, about 250 people gathered at the West Side Institutional Synagogue, a Modern Orthodox shul in Manhattan, to mark the 20th anniversary of Kahane's death. Shannon Taylor, a lawyer who organised speaking engagements for the rabbi, says Lance's exposé of the Al Qaeda link was a catalyst for the event.

Taylor, who was at the Marriott Hotel the night Kahane was killed, observes: "I thought that there was nothing more to discover. But justice requires that the truth has to be found and put to rest."